In state of the art, changing the appliance to the service mode is done by pressing the buttons on the appliance in a predefined combination with a predefined sequence or by entering a code. In the state of the art, the details of such applications are disclosed in the patent applications of German no DE19505485, European no EP1030235 and no EP0978773, international no WO993296 and no WO9924882.
However, in these applications, the user, even though not aiming to do so, can unintentionally change the appliance to the service mode by pressing the said key combination successively or entering the defined code during the process.
In the German patent application no. DE19850860, in addition to the button combination to be pressed for changing the appliance to the service mode etc., the appliance being brought into a condition, which is unlikely in the usual rest, and operating conditions, for example opening the upper plate is suggested in order to prevent this problem. Since the user will not open the upper plate during normal use, then bringing the machine to the service mode unintentionally will be out of the question. However, in the said implementation, bringing the appliance to a mode which is unlikely in the usual rest and operating conditions can create hardships for the maintenance personnel.